His comments come as militant group ISIL extends its path of bloodshed in Iraq after crossing the border from war-torn Syria.

The group is using online recruitment videos to entice Muslims in Australia and other parts of the world to join the fight.

Obama has told CNN the past few years have seen jihadists from Europe and as far as Australia going to Syria to get trained and then going back to their home countries.

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Reports say up 300 Australians have entered Syria to fight and Prime Minister Tony Abbott warns they must be stopped from re-entering Australia.

Fairfax Media on Sunday reported how young Australians were showing their support for fighters in Syria and Iraq by liking images, creating online groups and adopting the black-and-white flag used by a terrorist group on their social media pages.

The support coincides with the release of an online recruitment video featuring two Australians, one of whom is since believed to have been killed in the fighting.

Sources have told The Sun-Herald that one of the men is believed to be Zakaria Raad, who was with Islamic State of Iraq and the Levant (also known as ISIS) and preparing to go from Syria to Iraq. He was believed to have been killed in an ambush in Syria and was understood to be the same man who was involved in the whipping of a Muslim man as punishment under sharia.

Channel Ten last night reported the same connections.

Instagram, Twitter and Facebook accounts set up by people in Sydney and Melbourne are carrying images of armed fighters, the flag used by the ISIL and messages of support for the ‘‘mujaheddin’’. Some of the images are accompanied by slogans such as ‘‘Live by it, die by it’’. One picture shows a gun and a passport, with the superimposed words: ‘‘That one way ticket to Jannah (heaven).’’

An Australian Twitter account in support of the insurgents says: ‘‘ISIS is fighting for the law of God and freedom, 100% support from Australia, The Media is all lies, the people love ISIS.’’ An Instagram account in the name of ISIL says ‘‘creating awareness of the true mujaheddin that have sacrificed everything for justice (share the page)’’.

One Sydney woman, who has adopted the ISIL insignia as her cover photo on her Facebook page, had her Instagram account suspended on Friday. Hers is one of several social media accounts that have been shut down in recent weeks, angering people who feel they have been denied their right to voice an opinion.

The Twitter account jnob_isis was suspended last week, attracting angry comments such as ‘‘Another #ISIS official account was suspended by Kufr [non-believers]’’.

Six other Twitter accounts are also known to have been shut down. But it appears that as soon as one account is shut down, another one opens A new group was formed in western Sydney this month by a student who uses the ISIL flag as his profile picture.

Amid the online activity, a petition was launched asking for Twitter to block all ISIL-related accounts.

In the past few days, graphic images of executions in Iraq have emerged, along with claims that Australians may have been involved.

The federal government believes up to 100 Australians are fighting in Iraq and Syria, and Prime Minister Tony Abbott has vowed to take firm action against anyone returning home who has been fighting with extremist groups, including ISIL.

On Friday a video, which has been reported on by the ABC and is believed to have been made weeks ago in Syria, emerged featuring two men – Abu Yahya ash Shami (believed to be Raad) and Abu Nour al-Iraqi – who identified themselves as Australians.

The video, mostly recorded in English and titled ‘‘There is No Life without Jihad’’, was apparently posted online by members of ISIL. It shows men carrying weapons, walking through bush and attending meetings, and encourages Australians and Americans to join the fight.

Subtitles on the video indicate that Abu Yahya ash Shami, who is believed to have come from Sydney, was killed some time after the video was made.